Where is the anacrontab log?

You can access the anacrontab like this:

awk '/anacron/' /var/log/syslog | less

Result:

root@Odin:~# awk '/anacron/' /var/log/syslog
Nov 21 08:11:58 Odin anacron[877]: Job `cron.daily' terminated
Nov 21 08:11:58 Odin anacron[877]: Normal exit (1 job run)
Nov 21 18:42:13 Odin systemd[1]: Started Run anacron jobs.
Nov 21 18:42:13 Odin anacron[845]: Anacron 2.3 started on 2016-11-21
Nov 21 18:42:13 Odin anacron[845]: Normal exit (0 jobs run)
Nov 21 20:38:31 Odin systemd[1]: Started Run anacron jobs.
Nov 21 20:38:31 Odin anacron[770]: Anacron 2.3 started on 2016-11-21
Nov 21 20:38:31 Odin anacron[770]: Will run job `db.backup' in 60 min.
Nov 21 20:38:31 Odin anacron[770]: Will run job `daglig.backup' in 200 min.
Nov 21 20:38:31 Odin anacron[770]: Jobs will be executed sequentially
Nov 21 21:05:50 Odin systemd[1]: Started Run anacron jobs.
Nov 21 21:05:50 Odin anacron[833]: Anacron 2.3 started on 2016-11-21
Nov 21 21:05:50 Odin anacron[833]: Will run job `test' in 1 min.
Nov 21 21:05:50 Odin anacron[833]: Will run job `db.backup' in 60 min.
Nov 21 21:05:50 Odin anacron[833]: Will run job `daglig.backup' in 200 min.
Nov 21 21:05:50 Odin anacron[833]: Jobs will be executed sequentially
Nov 21 20:07:06 Odin anacron[833]: Job `test' started
Nov 21 20:07:06 Odin anacron[833]: Job `test' terminated
Nov 21 22:05:50 Odin anacron[833]: Job `db.backup' started

Nov 21 22:05:50 Odin anacron[833]: Job `db.backup' terminated